linux-kernel - Re: [PATCH] RDS: fix race condition when sending a message on unbound socket.

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Message-ID: <56213845.6020900@oracle.com>
Date:	Fri, 16 Oct 2015 10:47:49 -0700
From:	santosh shilimkar <santosh.shilimkar@...cle.com>
To:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	Vegard Nossum <vegard.nossum@...cle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Chien Yen <chien.yen@...cle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] RDS: fix race condition when sending a message on unbound
 socket.

On 10/16/2015 8:11 AM, Quentin Casasnovas wrote:
> Sasha's found a NULL pointer dereference in the RDS connection code when
> sending a message to an apparently unbound socket.  The problem is caused
> by the code checking if the socket is bound in rds_sendmsg(), which checks
> the rs_bound_addr field without taking a lock on the socket.  This opens a
> race where rs_bound_addr is temporarily set but where the transport is not
> in rds_bind(), leading to a NULL pointer dereference when trying to
> dereference 'trans' in __rds_conn_create().
>
> Vegard wrote a reproducer for this issue, so kindly ask him to share if
> you're interested.
>
> I cannot reproduce the NULL pointer dereference using Vegard's reproducer
> with this patch, whereas I could without.
>
> Complete earlier incomplete fix to CVE-2015-6937:
>
>    74e98eb08588 ("RDS: verify the underlying transport exists before creating a connection")
>
> Signed-off-by: Quentin Casasnovas <quentin.casasnovas@...cle.com>
> Reviewed-by: Vegard Nossum <vegard.nossum@...cle.com>
> Reviewed-by: Sasha Levin <sasha.levin@...cle.com>
> Cc: Vegard Nossum <vegard.nossum@...cle.com>
> Cc: Sasha Levin <sasha.levin@...cle.com>
> Cc: Chien Yen <chien.yen@...cle.com>
> Cc: Santosh Shilimkar <santosh.shilimkar@...cle.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: stable@...r.kernel.org
> ---
Looks right. Am glad that we got deference issue as well as
the bind race fixed with it. Mail sent to Vegard for his test
case which I would like to add to my tests. Thanks for the fix.

FWIW,
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>

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